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Kinds of Texas Terms modified by Texas Selected AbstractsTEMPORAL PATTERN OF AFRICANIZATION IN A FERAL HONEYBEE POPULATION FROM TEXAS INFERRED FROM MITOCHONDRIAL DNAEVOLUTION, Issue 5 2004M. Alice Pinto Abstract The invasion of Africanized honeybees (Apis mellifera L.) in the Americas provides a window of opportunity to study the dynamics of secondary contact of subspecies of bees that evolved in allopatry in ecologically distinctive habitats of the Old World. We report here the results of an 11-year mitochondrial DNA survey of a feral honeybee population from southern United States (Texas). The mitochondrial haplotype (mitotype) frequencies changed radically during the 11-year study period. Prior to immigration of Africanized honeybees, the resident population was essentially of eastern and western European maternal ancestry. Three years after detection of the first Africanized swarm there was a mitotype turnover in the population from predominantly eastern European to predominantly A. m. scutellata (ancestor of Africanized honeybees). This remarkable change in the mitotype composition coincided with arrival of the parasitic mite Varroa destructor, which was likely responsible for severe losses experienced by colonies of European ancestry. From 1997 onward the population stabilized with most colonies of A. m. scutellata maternal origin. [source] A NEW LYNGBYA SPECIES FROM AQUARENA SPRINGS, SAN MARCOS, TEXASJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Mills, J. T.1 & Johansen, J. R.2 1Department of Biology, St. Edwards University, Austin, TX 78704.USA; 2Department of Biology, John Carroll University, University Heights, OH 44118 USA A large Lyngbya species was isolated from Aquarena Springs, a series of freshwater, nonmineral springs flowing from the Edwards Aquifer that are impounded to form Spring Lake. The species grows in rather large, loosely formed clumps at a depth of 2-3 meters, and consists of sheathed filaments from 55 to 60 um in thickness containing a single trichome that ranges from 45-50 um in thickness in each sheath. The sheath is 5-6um thick. Our isolate is similar to Plectonema wollei Farlow ex Gomont, a large, thick sheathed morphospecies which has recently been placed in Lyngbya wollei (Farlow ex Gomont) Onodera et al. It is also similar to Blennothrix species, another large-trichomed genus with a distinctive form of false branching. However, the Lyngbya from Aquarena Springs shows no evidence of false branching of any type, forms loose clusters rather than mats, and is larger than any of the species currently described in any of the genera in question. When we sequenced the 16SrRNA and associated 16S-23S internal transcribed spacer (ITS), phylogenetic analysis indicated the taxon was most similar to Oscillatoria sanctae. However, there are so few taxa in the Oscillatoriaceae sensu stricto that have been sequenced, phylogenetic placement of the taxon by molecular analysis alone is not possible at present. Two different ITS configurations were obtained, one with both the tRNA "Ile" gene and the tRNA "Ala" gene, the other with no tRNA genes. Our work represents the first molecular analysis of any form in the large-trichomed Lyngbya clade. [source] SPECIES COMPOSITION AND SEASONAL PERIODICITY OF MACROALGAL SPECIES IN CORPUS CHRISTI BAY, TEXASJOURNAL OF PHYCOLOGY, Issue 2000J.C. Agan Benthic algal sampling from selected sites along Corpus Christi Bay and from one site at the Port Aransas, Texas south jetty was completed between April 1999 and February, 2000. Species composition, seasonal periodicity, and fluctuations in temperature and salinity were determined. This is the first comprehensive study of benthic macroalgae conducted in Corpus Christi Bay, which is shallow, turbid, and lacks natural hard substrate. Man-made jetties are necessary for suitable floral attachment. Macroalgae are affected by changes in salinity as freshwater inflows are followed by periods of drought, which increase salinity. These effects are most notable where freshwater enters at the south end near Oso Bay and at the north end at Nueces Bay. Previous Texas algal collections described species of Enteromorpha, Ulva, Gelidium, and Gracilaria as the most dominant plants of the area. This supports the current study with the additions of Hypnea musciformis and Centroceras clavulatum. Dominant plants at the Port Aransas jetty include Ulva fasciata, Padina gymnospora, and Hypnea musciformis. The Rhodophyta including Gracilaria, Gelidium, and Centroceras clavulatum dominate the bay and do so throughout the year. Chlorophytes, although few in species richness, are important to benthic coverage and biomass. Phaeophyta are found predominantly at the Port Aransas jetty with Sargassum, Dictyota dichotoma, and Petalonia fascia being most abundant. A transition occurs in species composition as the water temperature changes seasonally. Hincksia, Ectocarpus, and Petalonia fascia are found only during the cooler months. [source] GROUPWISE MODELING STUDY OF BACTERIALLY IMPAIRED WATERSHEDS IN TEXAS: CLUSTERING ANALYSIS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2006Sabu Paul ABSTRACT: Under the Clean Water Act (CWA) program, the Texas Commission on Environmental Quality (TCEQ) listed 110 stream segments in the year 2000 with pathogenic bacteria impairment. A study was conducted to evaluate the probable sources of pollution and characterize the watersheds associated with these impaired water bodies. The primary aim of the study was to group the water bodies into clusters having similar watershed characteristics and to examine the possibility of studying them as a group by choosing models for total maximum daily load (TMDL) development based on their characteristics. This approach will help to identify possible sources and determine appropriate models and hence reduce the number of required TMDL studies. This in turn will help in reducing the effort required to restore the health of the impaired water bodies in Texas. The main characteristics considered for the classification of water bodies were land use distribution within the watershed, density of stream network, average distance of land of a particular use to the closest stream, household population, density of on-site sewage facilities (OSSFs), bacterial loading from different types of farm animals and wildlife, and average climatic conditions. The climatic data and observed instream fecal coliform bacteria concentrations were analyzed to evaluate seasonal variability of instream water quality. The grouping of water bodies was carried out using the multivariate statistical techniques of factor analysis/principal component analysis, cluster analysis, and discriminant analysis. The multivariate statistical analysis resulted in six clusters of water bodies. The main factors that differentiated the clusters were found to be bacterial contribution from farm animals and wildlife, density of OSSFs, density of households connected to public sewers, and land use distribution. [source] A TRIANGULAR MODEL OF DIMENSIONLESS RUNOFF PRODUCING RAINFALL HYETOGRAPHS IN TEXAS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2003William H. Asquith ABSTRACT: A synthetic triangular hyetograph for a large data base of Texas rainfall and runoff is needed. A hyetograph represents the temporal distribution of rainfall intensity at a point or over a watershed during a storm. Synthetic hyetographs are estimates of the expected time distribution for a design storm and principally are used in small watershed hydraulic structure design. A data base of more than 1,600 observed cumulative hyetographs that produced runoff from 91 small watersheds (generally less than about 50 km2) was used to provide statistical parameters for a simple triangular shaped hyetograph model. The model provides an estimate of the average hyetograph in dimensionless form for storm durations of 0 to 24 hours and 24 to 72 hours. As a result of this study, the authors concluded that the expected dimensionless cumulative hyetographs of 0 to 12 hour and 12 to 24 hour durations were sufficiently similar to be combined with minimal information loss. The analysis also suggests that dimensionless cumulative hyetographs are independent of the frequency level or return period of total storm depth and thus are readily used for many design applications. The two triangular hyetographs presented are intended to enhance small watershed design practice in applicable parts of Texas. [source] ADJUSTMENT OF STREAM CHANNEL CAPACITY FOLLOWING DAM CLOSURE, YEGUA CREEK, TEXAS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2002Anne Chin ABSTRACT: In Yegua Creek, a principal tributary of the Brazos River in Texas, surveys of a 19 km channel reach downstream of Somerville Dam show that channel capacity decreased by an average of 65 percent in a 34 year period following dam closure. The decrease corresponds with an approximately 85 percent reduction in annual flood peaks. Channel depth has changed the most, decreasing by an average of 61 percent. Channel width remained stable with an average decrease of only 9 percent, reflecting cohesive bank materials along with the growth of riparian vegetation resulting from increased low flows during dry summer months. Although large changes in stream channel geometry are not uncommon downstream of dams, such pronounced reductions in channel capacity could have long-term implications for sediment delivery through the system. [source] ANACORACID SHARKS FROM THE ALBIAN (LOWER CRETACEOUS) PAWPAW SHALE OF TEXASPALAEONTOLOGY, Issue 4 2007MIKAEL SIVERSON Abstract:, Recent collecting from the Pawpaw Shale in north-east Texas has yielded several hundred teeth of anacoracid sharks. The material allows for a much-needed revision of the Late Albian anacoracids from North America. The previously recognized Squalicorax sp., also referred to as S. volgensis in more recent publications, is a mix of two different species: S. priscoserratus sp. nov. and S. pawpawensis sp. nov. In addition to these two new species, a single tooth is assigned to S. aff. S. baharijensis. Our data indicate that anacoracids were a considerably more diverse group in the North American Cretaceous than previously thought. We attribute much of the underestimation of diversity to vague species concepts, poor preparation techniques and the associated lack of attention to certain dental features, in particular neck morphology, root surface porosity and the root's vascularization. [source] REPLENISHINGTHE SOILANDTHE SOULOF TEXAS: THE CIVILIAN CONSERVATION CORPSINTHE LONE STAR STATEASAN EXAMPLEOF STATE -FEDERAL WORK RELIEF DURINGTHE GREAT DEPRESSIONTHE HISTORIAN, Issue 4 2003KENNETH E. HENDRICKSON JR. First page of article [source] COMPENSATORY RESTORATION IN A RANDOM UTILITY MODEL OF RECREATION DEMANDCONTEMPORARY ECONOMIC POLICY, Issue 4 2010GEORGE R. PARSONS Natural Resource Damage Assessment cases often call for compensation in non-monetary or restoration equivalent terms. In this article, we present an approach that uses a conventional economic model, a travel cost random utility model of site choice, to determine compensatory restoration equivalents for hypothetical beach closures on the Gulf Coast of Texas. Our focus is on closures of beaches on the Padre Island National Seashore and compensation for day-trip users. We identify restoration projects that compensate for beach closures and that have good alignment in terms of compensating those who actually suffer from the closures. (JEL Q26) [source] THE SHORT-TERM EFFECTS OF EXECUTIONS ON HOMICIDES: DETERRENCE, DISPLACEMENT, OR BOTH?,CRIMINOLOGY, Issue 4 2009KENNETH C. LAND Does the death penalty save lives? In recent years, a new round of research has been using annual time-series panel data from the 50 U.S. states for 25 or so years from the 1970s to the late 1990s that claims to find many lives saved through reductions in subsequent homicide rates after executions. This research, in turn, has produced a round of critiques, which concludes that these findings are not robust enough to model even small changes in specifications that yield dramatically different results. A principal reason for this sensitivity of the findings is that few state-years exist (about 1 percent of all state-years) in which six or more executions have occurred. To provide a different perspective, we focus on Texas, a state that has used the death penalty with sufficient frequency to make possible relatively stable estimates of the homicide response to executions. In addition, we narrow the observation intervals for recording executions and homicides from the annual calendar year to monthly intervals. Based on time-series analyses and independent-validation tests, our best-fitting model shows that, from January 1994 through December 2005, evidence exists of modest, short-term reductions in homicides in Texas in the first and fourth months that follow an execution,about 2.5 fewer homicides total. Another model suggests, however, that in addition to homicide reductions, some displacement of homicides may be possible from one month to another in the months after an execution, which reduces the total reduction in homicides after an execution to about .5 during a 12-month period. Implications for additional research and the need for future analysis and replication are discussed. [source] Corporate Chickens and Community Conflict in East TexasCULTURE, AGRICULTURE, FOOD & ENVIRONMENT, Issue 1 2005Douglas H. Constance First page of article [source] Human-Peyote Interaction in South TexasCULTURE, AGRICULTURE, FOOD & ENVIRONMENT, Issue 1 2000Servando Z. Hinojosa First page of article [source] Teacher Identity and Agency in School Worlds: Beyond the All-Good/All-Bad Discourse on Accountability-Explicit Curriculum PoliciesCURRICULUM INQUIRY, Issue 2 2006KRIS SLOAN ABSTRACT Drawing on case studies of three elementary school teachers in a diverse urban school setting in Texas, the author explores the varied ways teachers actively read accountability-related curriculum policies and then respond to these policies. Rooted in classroom observations and extensive teacher interviews, the author examines issues of teacher identity and identity formation as a base from which to explore teacher agency vis-ŕ-vis accountability-explicit curriculum policies. His analysis suggests that (1) individual teachers actively read and respond to locally conceived accountability-explicit curriculum policies in varied, perhaps even unique, ways; (2) teacher identities are powerful means through which to understand these varied experiences with and responses to accountability-explicit curriculum policies; and (3) current understandings of teacher agency vis-ŕ-vis accountability-explicit curriculum policies as merely a capacity to resist,as does much of the literature that is critical of accountability,obfuscates important issues of teacher quality and equity. [source] Social vulnerability and the natural and built environment: a model of flood casualties in TexasDISASTERS, Issue 4 2008Sammy Zahran Studies on the impacts of hurricanes, tropical storms, and tornados indicate that poor communities of colour suffer disproportionately in human death and injury., Few quantitative studies have been conducted on the degree to which flood events affect socially vulnerable populations. We address this research void by analysing 832 countywide flood events in Texas from 1997,2001. Specifically, we examine whether geographic localities characterised by high percentages of socially vulnerable populations experience significantly more casualties due to flood events, adjusting for characteristics of the natural and built environment. Zero-inflated negative binomial regression models indicate that the odds of a flood casualty increase with the level of precipitation on the day of a flood event, flood duration, property damage caused by the flood, population density, and the presence of socially vulnerable populations. Odds decrease with the number of dams, the level of precipitation on the day before a recorded flood event, and the extent to which localities have enacted flood mitigation strategies. The study concludes with comments on hazard-resilient communities and protection of casualty-prone populations. [source] Forest blowdown impacts of Hurricane Rita on fluvial systemsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2009Jonathan D. Phillips Abstract Hurricane Rita, a category three hurricane which struck the US Gulf Coast near the Louisiana/Texas border in 2005, did not cause extensive river flooding. However, the storm did result in extensive forest damage and tree blowdown. High-resolution post-storm aerial photography allowed an inventory of river bank trees blown into the channel along the lower Neches and Sabine Rivers of southeast Texas and southwest Louisiana. Blowdowns directly into the channel averaged 9·3 per kilometer in the lower Neches and 13·4 in the lower Sabine River, but individual reaches 10 to 20 km in length had rates of 20 to 44 blowdowns per kilometer. Though large woody debris (LWD) from Hurricane Rita was widely perceived to reduce the capacity of channels to convey flow, no strong evidence exists of increased flooding or significant reductions in channel conveyance capacity due to LWD from the storm. The Rita blowdown inventory also allowed an assessment of whether similar blowdown events could account for major logjams and rafts on Red, Atchafalaya, and Colorado Rivers on the Gulf Coast, which blocked navigation from tens to hundreds of kilometers in the 1800s. Results from Hurricane Rita suggest that blowdown into channels alone , not withstanding blowdown elsewhere in the river valleys or along tributaries which could deliver LWD to the river , is sufficient to completely block channels, thus providing a plausible mechanism for initiating such (pre)historic log rafts. Copyright © 2009 John Wiley & Sons, Ltd. [source] Optical remote mapping of rivers at sub-meter resolutions and watershed extentsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2008W. Andrew Marcus Abstract At watershed extents, our understanding of river form, process and function is largely based on locally intensive mapping of river reaches, or on spatially extensive but low density data scattered throughout a watershed (e.g. cross sections). The net effect has been to characterize streams as discontinuous systems. Recent advances in optical remote sensing of rivers indicate that it should now be possible to generate accurate and continuous maps of in-stream habitats, depths, algae, wood, stream power and other features at sub-meter resolutions across entire watersheds so long as the water is clear and the aerial view is unobstructed. Such maps would transform river science and management by providing improved data, better models and explanation, and enhanced applications. Obstacles to achieving this vision include variations in optics associated with shadows, water clarity, variable substrates and target,sun angle geometry. Logistical obstacles are primarily due to the reliance of existing ground validation procedures on time-of-flight field measurements, which are impossible to accomplish at watershed extents, particularly in large and difficult to access river basins. Philosophical issues must also be addressed that relate to the expectations around accuracy assessment, the need for and utility of physically based models to evaluate remote sensing results and the ethics of revealing information about river resources at fine spatial resolutions. Despite these obstacles and issues, catchment extent remote river mapping is now feasible, as is demonstrated by a proof-of-concept example for the Nueces River, Texas, and examples of how different image types (radar, lidar, thermal) could be merged with optical imagery. The greatest obstacle to development and implementation of more remote sensing, catchment scale ,river observatories' is the absence of broadly based funding initiatives to support collaborative research by multiple investigators in different river settings. Copyright © 2007 John Wiley & Sons, Ltd. [source] A method for establishing the critical threshold for aeolian transport in the fieldEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2004John E. Stout Abstract A basic feature of any wind-eroding surface is its threshold , the wind speed at which sediment transport is initiated. A new method was developed and tested that allows for the rapid determination of threshold under natural wind conditions in the ,eld. A mathematical expression that relates saltation activity and relative wind strength was reformulated so that threshold may be calculated from measurements of saltation activity and the mean and standard deviation of wind speed. To test the new method and determine its usefulness, a ,eld experiment was performed within a region of low-relief dunes on the Southern High Plains of West Texas. The experimental system consisted of a 2-m meteorological tower and a piezoelectric saltation sensor. It was found that during periods of active aeolian activity, threshold values could be calculated every 5 minutes. This new method allows for routine monitoring of surface threshold conditions in the ,eld. Example threshold calculations are presented and they demonstrate that the method works well. Published in 2004 by John Wiley & Sons, Ltd. [source] Resource discovery in ant communities: do food type and quantity matter?ECOLOGICAL ENTOMOLOGY, Issue 5 2010JESSICA M. C. PEARCE-DUVET 1. Omnivorous woodland ant species trade off between the ability to find and behaviourally control food resources. Dominant species can limit the ability of subordinates to harvest certain food items. However, subordinate species, by being faster discoverers, could gain access to such food items by arriving at them first. 2. In this study, we tested the hypothesis that resource-directed discovery occurs in ant communities and that good discoverers preferentially discover high value resources. We did this by measuring time to discovery and the number of discoveries of high and low levels of two resource types, crickets and honey, for species occurring in Texas and Arizona woodland ant communities. 3. Ants discovered resources roughly 10 times faster in Texas than in Arizona. They discovered crickets more rapidly than honey in both communities, but there was no difference in the discovery of different resource levels. We also found that species were not biased in their discovery of different resource types or levels. 4. These results provide indirect evidence that discovery is directed by resource stimuli but that such directedness does not impact interspecific exploitative competition. [source] Genetic differences in growth of an invasive tree speciesECOLOGY LETTERS, Issue 6 2001Evan Siemann Invasive plants are often more vigorous in their introduced ranges than in their native ranges. This may reflect an innate superiority of plants from some habitats or an escape from their enemies. Another hypothesis proposes that invasive plants evolve increased competitive ability in their introduced range. We present the results of a 14-year common garden experiment with the Chinese Tallow Tree (Sapium sebiferum) from its native range (Asia), place of introduction to North America (Georgia) and areas colonized a century later (Louisiana and Texas). Invasive genotypes, especially those from recently colonized areas, were larger than native genotypes and more likely to produce seeds but had lower quality, poorly defended leaves. Our results demonstrate significant post-invasion genetic differences in an invasive plant species. Post-introduction adaptation by introduced plants may contribute to their invasive success and make it difficult to predict problem species. [source] Seasonal and spatial variation in a prairie stream-fish assemblageECOLOGY OF FRESHWATER FISH, Issue 3 2002K. G. Ostrand Abstract,,,Stream-fish assemblage and environmental data for 13 sites in the upper Brazos River, Texas, USA during 1997 and 1998 were used to assess the relationship between environmental conditions, and seasonal and spatial variation in fish species abundance and distribution patterns. There was considerable spatial variation in environmental conditions among sites. Spatial variation in species diversity and species composition was related to variation in conductance (salinity), depth and current velocity among sites and streams. Species diversity increased downstream and species composition shifted from primarily cyprinodontids upstream to cyprinids downstream. Among all dominant species, spatial components of variation in fish abundance were greater than seasonal components, suggesting that assemblage structure is determined more by average or persistent differences in environmental conditions among sites than by seasonal variation in environmental conditions. [source] Impacts of aircraft deicer and anti-icer runoff on receiving waters from Dallas/Fort worth International Airport, Texas, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2006Steven R. Corsi Abstract From October 2002 to April 2004, data were collected from Dallas/Fort Worth (DFW) International Airport (TX, USA) outfalls and receiving waters (Trigg Lake and Big Bear Creek) to document the magnitude and potential effects of aircraft deicer and anti-icer fluid (ADAF) runoff on water quality. Glycol concentrations at outfalls ranged from less than 18 to 23,800 mg/L, whereas concentrations in Big Bear Creek were less because of dilution, dispersion, and degradation, ranging from less than 18 to 230 mg/L. Annual loading results indicate that 10 and 35% of what was applied to aircraft was discharged to Big Bear Creek in 2003 and 2004, respectively. Glycol that entered Trigg Lake was diluted and degraded before reaching the lake outlet. Dissolved oxygen (DO) concentrations at airport outfalls sometimes were low (<2.0 mg/L) but typical of what was measured in an urban reference stream. In comparison, the DO concentration at Trigg Lake monitoring sites was consistently greater than 5.5 mg/L during the monitoring period, probably because of the installation of aerators in the lake by DFW personnel. The DO concentration in Big Bear Creek was very similar at sites upstream and downstream of airport influence (>5.0 mg/L). Results of toxicity tests indicate that effects on Ceriodaphnia dubia, Pimephales promelas, and Selanastrum capricornutum are influenced by type IV ADAF (anti-icer), not just type I ADAF (deicer) as is more commonly assumed. [source] Organochlorine pesticides and mercury in cottonmouths (Agkistrodon piscivorus) from northeastern Texas, USA,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2005Thomas R. Rainwater Abstract Dspite their ecological importance andglobal decline, snakes remain poorly studied in ecotoxicology. In this study, we examined organochlorine (OC) pesticide and mercury accumulation in cottonmouths (Agkistrodon piscivorus) living on a contaminated site in northeastern Texas (USA). Mercury and p,p,-dichlorodiphenyldichloroethylene (p,p,-DDE) were detected in all snakes examined. Other OCs, including p,p,-dichlorodiphenyltrichloroethane (p,p,-DDT), methoxychlor, aldrin, and heptachlor, also were detected, but less frequently. Concentrations of p,p,-DDE were higher in fat than in liver, while mercury concentrations were highest in liver, followed by kidney and tail clips. One animal contained the highest mercury concentration yet reported for a snake (8,610 ng/g). Mercury concentrations in liver and kidney were higher in males than females, while no intersex differences in p,p,-DDE concentrations were observed. Concentrations of p,p,-DDE in fat were correlated positively with body size in male cottonmouths but not females, suggesting a slower rate of accumulation in females. Body size strongly predicted mercury concentrations in liver, kidney, and tail clips of both sexes. Tail clips were strong predictors of mercury in liver and kidney in males but not females, suggesting possible sex-dependent differences in mercury toxicokinetics. Both long-term field studies and controlled laboratory investigations are needed to adequately assess the response of cottonmouths to chronic contaminant exposure. [source] Relationship between lysosomal membrane destabilization and chemical body burden in eastern oysters (Crassostrea virginica) from Galveston Bay, Texas, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2002Hyun-Min Hwang Abstract Lysosomal destabilization was measured by using hemocytes of eastern oysters (Crassostrea virginica) collected along a chemical concentration gradient in Galveston Bay, Texas, USA. Results of the lysosomal response were compared to concentrations of organic compounds and trace elements in oyster tissue. Concentrations (on a dry-wt basis) ranged from 288 to 2,390 ng/g for polycyclic aromatic hydrocarbons (PAHs), 38 to 877 ng Sn/g for tri- n -butyltin (TBT), 60 to 562 ng/g for polyclorinated biphenyls (PCBs), and 7 to 71 ng/g for total DDT. Trace element concentrations (on a dry-wt basis) ranged from 1.1 to 4.0 ,g/g for Cd, 105 to 229 ,g/g for Cu, 212 to 868 ,g/g for Al, and 1,200 to 8,180 ,g/g for Zn. The percentage of destabilized lysosomes ranged from 34 to 81%. A significant positive correlation (p < 0.05) was observed between lysosomal destabilization and body burden of organic compounds (PAHs, PCBs, TBT, and chlorinated pesticides). No significant correlation was found between metal concentrations and lysosomal destabilization. Based on lysosomal destabilization, the study sites in Galveston Bay can be placed in one of three groups: healthy (Hanna Reef and Confederate Bay), moderately damaged (Offats Bayou and Todd's Dump), and highly damaged (Yacht Club and Ship Channel). Lysosomal destabilization that is consistent with toxic chemical body burdens supports previous observations that lysosomal membranes are damaged by toxic chemicals and indicates that this method can serve as an early screening tool to assess overall ecosystem health by using oysters. [source] Clustering composition vectors using uncertainty informationENVIRONMETRICS, Issue 8 2007William F. Christensen Abstract In the biological and environmental sciences, interest often lies in using multivariate observations to discover natural clusters of objects. In this manuscript, the incorporation of measurement uncertainty information into a cluster analysis is discussed. This study is motivated by a problem involving the clustering of composition vectors associated with each of several chemical species. The observed abundance of each component is available along with its estimated uncertainty (measurement error standard deviation). An approach is proposed for converting the abundance vectors into composition (relative abundance) vectors, obtaining the covariance matrix associated with each composition vector, and defining a Mahalanobis distance between composition vectors that are suitable for cluster analysis. The approach is illustrated using particle size distributions obtained near Houston, Texas in 2000. Computer simulation is used to compare the performance of Mahalanobis-distance-based and Euclidean-distance-based clustering approaches. The use of a modified Mahalanobis distance along with Ward's method is recommended for use. Copyright © 2007 John Wiley & Sons, Ltd. [source] A cost-effective simulation curriculum for preclinical endodonticsEUROPEAN JOURNAL OF DENTAL EDUCATION, Issue 1 2004Roberta Pileggi A challenge in contemporary dental education is to achieve a smooth transition from preclinical teaching environments to patient-care clinics in a cost-effective manner. The preclinical endodontic courses at The University of Texas, Dental Branch at Houston provide a unique learning environment that enables the student to perform endodontic treatment on extracted teeth in a typodont, and be involved in diagnosis and treatment-planning discussions. The specially designed stone typodont used has built-in radiographic capability, and is mounted at each chair in the clinic. During each preclinical session, students are assigned clinical cubicles and proper aseptic protocol is followed. Students are required to wear gloves, masks and eyewear, and place a rubber dam during treatment. Written self-assessment evaluations based upon prescribed criteria are utilised; feedback is given by faculty composed of both full-time endodontists and graduate students who periodically rotate and are calibrated on a regular basis. In the lecture phase, clinical case scenarios are presented to reinforce concepts of diagnosis and emergency care and to help integrate endodontics with other disciplines; a Socratic-like teaching style is established by the faculty facilitator to create an environment for developing critical-thinking and problem-solving skills. The overall feedback from graduating students has been very positive. Advantages of this format are an easier transition to patient management, a more keen interest in specialsation and a perceived increase in levels of confidence. [source] TEMPORAL PATTERN OF AFRICANIZATION IN A FERAL HONEYBEE POPULATION FROM TEXAS INFERRED FROM MITOCHONDRIAL DNAEVOLUTION, Issue 5 2004M. Alice Pinto Abstract The invasion of Africanized honeybees (Apis mellifera L.) in the Americas provides a window of opportunity to study the dynamics of secondary contact of subspecies of bees that evolved in allopatry in ecologically distinctive habitats of the Old World. We report here the results of an 11-year mitochondrial DNA survey of a feral honeybee population from southern United States (Texas). The mitochondrial haplotype (mitotype) frequencies changed radically during the 11-year study period. Prior to immigration of Africanized honeybees, the resident population was essentially of eastern and western European maternal ancestry. Three years after detection of the first Africanized swarm there was a mitotype turnover in the population from predominantly eastern European to predominantly A. m. scutellata (ancestor of Africanized honeybees). This remarkable change in the mitotype composition coincided with arrival of the parasitic mite Varroa destructor, which was likely responsible for severe losses experienced by colonies of European ancestry. From 1997 onward the population stabilized with most colonies of A. m. scutellata maternal origin. [source] TURNING OFFENDERS INTO RESPONSIBLE PARENTS AND CHILD SUPPORT PAYERS,FAMILY COURT REVIEW, Issue 3 2005Esther Ann Griswold This article describes four demonstration projects that strive to promote responsible behavior with respect to parenting, child support payment, and employment among incarcerated and paroled parents with child support obligations. These projects, conducted in Colorado, Illinois, Massachusetts, and Texas, with support from the federal Office of Child Support Enforcement and evaluated by the Center for Policy Research, led to a number of common outcomes and lessons. The projects revealed that inmates want help with child support, parenting, and employment and that prisons can be effective settings in which to conduct such interventions. Family reintegration programs were popular with inmates and may have helped to avoid the rupture of parent,child relationships commonly associated with incarceration. Although employment is the key to child support payment following release, rates of postrelease employment and earnings at all project sites were low and the employment programs were of limited utility in helping released offenders find jobs. Agencies dealing with child support, employment, and criminal justice need to adopt more effective policies with incarcerated parents including transitional job programs that guarantee immediate, subsidized employment upon release, child support guidelines that adjust for low earnings, and better training and education opportunities during incarceration. [source] Simulating larval supply to estuarine nursery areas: how important are physical processes to the supply of larvae to the Aransas Pass Inlet?FISHERIES OCEANOGRAPHY, Issue 3 2004C. A. Brown Abstract Factors controlling the movement of fish larvae from coastal spawning environments to estuarine nursery areas are important to fish recruitment. In this paper, the role of physical processes in larval transport to estuarine nursery areas in the Aransas Pass region, Texas, is examined using a circulation model coupled with a fixed-depth particle transport model. Two phases of transport are examined: transport on the shelf to the tidal inlet and transport through the inlet to estuarine nursery areas. Observed pulsing in the supply of red drum (Sciaenops ocellatus) larvae to the tidal inlet is significantly correlated with modeled particle supply. This pulsing is not correlated with a specific physical process, but results from the interaction of several factors affecting water movement, including low-frequency variations in water level and wind forcing. Simulations suggest that the primary spawning region for red drum larvae that utilize nursery habitat in the Aransas Pass region is located north of the inlet. Patterns in the trajectories of particles that successfully enter the inlet reveal that they move alongshelf in the nearshore region and then move into the inlet, rather than moving directly across the shelf to the inlet. The approach path of particles outside the inlet determines the spatial transport patterns for inlets with branched channels and multiple bays. This study demonstrates that physical processes play an important role in determining larval supply to a tidal inlet. [source] African-American Students' Opinions About Foreign Language Study: An Exploratory Study of Low Enrollments at the College LevelFOREIGN LANGUAGE ANNALS, Issue 2 2005Zena Moore Abstract: Persistent low numbers of African Americans in the foreign language teacher certification program at the University of Texas at Austin motivated the study reported here. Two groups of students responded to a questionnaire that sought information on foreign language experience at elementary and high school, as well as family experiences in foreign languages. Findings revealed that whereas very few students had the opportunity to study a foreign language at the elementary level, all were exposed to at least a two-year compulsory program at high school. These experiences were not motivating enough to encourage college-level continuation, nor were family experiences. Students' language preferences did not support previous findings that low enrollment figures resulted from language offerings that lacked ethnic and cultural appeal. Rather, the study found that there appeared to be little effort made to encourage African-American high school and college students to consider teaching career paths. Students recommended more aggressive dissemination of information to African-American students at the college level about the advantages on pursuing foreign language study. They overwhelmingly suggested including a foreign language requirement in all discipline areas. [source] C3,C4 composition and prior carbon dioxide treatment regulate the response of grassland carbon and water fluxes to carbon dioxideFUNCTIONAL ECOLOGY, Issue 1 2007H. W. POLLEY Summary 1Plants usually respond to carbon dioxide (CO2) enrichment by increasing photosynthesis and reducing transpiration, but these initial responses to CO2 may not be sustained. 2During May, July and October 2000, we measured the effects of temporarily increasing or decreasing CO2 concentration by 150,200 µmol mol,1 on daytime net ecosystem CO2 exchange (NEE) and water flux (evapotranspiration, ET) of C3,C4 grassland in central Texas, USA that had been exposed for three growing seasons to a CO2 gradient from 200 to 560 µmol mol,1. Grassland grown at subambient CO2 (< 365 µmol mol,1) was exposed for 2 days to an elevated CO2 gradient (> 365 µmol mol,1). Grassland grown at elevated CO2 was exposed for 2 days to a subambient gradient. Our objective was to determine whether growth CO2 affected the amount by which grassland NEE and ET responded to CO2 switching (sensitivity to CO2). 3The NEE per unit of leaf area was greater (16,20%) and ET was smaller (9,20%), on average, at the higher CO2 concentration during CO2 switching in May and July. The amount by which NEE increased at the higher CO2 level was smaller at elevated than subambient growth concentrations on both dates, but relationships between NEE response and growth CO2 were weak. Conversely, the effect of temporary CO2 change on ET did not depend on growth CO2. 4The ratio of NEE at high CO2 to NEE at low CO2 during CO2 change in July increased from 1·0 to 1·26 as the contribution of C3 cover to total cover increased from 26% to 96%. Conversely, in May, temporary CO2 enrichment reduced ET more in C4 - than C3 -dominated grassland. 5For this mesic grassland, sensitivity of NEE and ET to brief change in CO2 depended as much on the C3,C4 composition of vegetation as on physiological adjustments related to prior CO2 exposure. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||